The invention is related to the commercial and residential construction industries and, in particular, to the ceramics industry.
Ceramic products of all types have been commonly used in society for thousands of years. The Greeks and Romans, among others, used ceramic tiles in temples and palaces. Some of these artistic mosaics can still be seen and appreciated in archeological sites.
Over the years, many different finishes and glazes have been applied on the surface of the ceramics to provide luster or protection. The ceramic body itself that makes up the tile, whiteware, or pitcher (or other ceramic product) is typically made of single clays or of a mixture of different clays, as is well known. Ceramics can be made from raw materials, such as clay, kaolin, feldspar, wollastonite, talc, calcium carbonate, dolomite and other known materials. It is now known how to formulate ceramics from synthetic materials. Binders are used, as necessary, to achieve the required mechanical strength.
After firing, the glaze on the surface of the ceramic develops a vitreous, transparent or opaque surface. It can be glossy or dull, based on the end application of the particular ceramic. Glazes typically have 3 components. First, they include a frit of some type which, during firing, fuses and forms a compact layer on the surface of the ceramic. Pigments can be used to impart a desired chromatic characteristic. Suspending agents are used to obtain specific theological effects in the product. Depending on the end product, various inorganic substances may be used to obtain special effects in the glaze.
The glaze is a fused facial finish on the surface of the ceramic. It generally has a vitreous covering that is substantially impervious after firing, so it serves to protect the ceramic. It is the properties of the glaze that gives color and beauty enhancement and also provides the surface sealing, water resistance, and other characteristics of the ceramic.
Generally, either single firing or double firing techniques are used to apply the glaze, as is well known. Glazes typically have one or more frits, fillers, pigments and other additives, as required.
Especially on ceramic tiles that are used in home bathrooms and kitchens, there is a need to have ceramics that glow in the dark. In this manner, some level of illumination is available for the late night walker without the need for turning on an overhead light or lamp.
Many people, especially the elderly, have a need to arise in the middle of the night and to visit the bathroom. Typically, it can be hard to fumble to find the switch for an overhead light or for a lamp. Besides, turning a light on will awaken other sleepers.
There are many useful purposes for a glow in the dark glaze applied to ceramic products, such as: light switches that glow in the dark; and glow in the dark ceramic tiles used as emergency signs.
Nonetheless, though there is clear benefit and need for glow in the dark ceramics, no one in the ceramics industry has ever utilized a glow in the dark glaze for ceramic products.
Therefore, ceramics coated with a night glow finish or glaze are quite desirable. One problem is that a phosphorescent pigment is needed for this purpose. At temperatures of 1300xc2x0 F. and higher, such phosphorescent pigments start to decompose. In order to properly mature non-leaded glazes, however, they must be fired at temperatures far above 1300xc2x0 F. Lead based glazes could theoretically be fired at temperatures below 1000xc2x0 F. to prevent the phosphorescent pigment from decomposing, but lead based glazes are prohibited in the USA due to health concerns.
Accordingly, the industry does not have an effective way to add phosphorescent pigments to ceramics glazes to achieve a night glow effect.
Therefore, it an object of this invention to provide a night glow ceramic glaze that includes a phosphorescent pigment, and which will not cause the phosphorescent pigment to decompose during firing. In a preferred embodiment, there is no lead, but the Invention also contemplates lead-based glazes with a phosphorescent pigment.
This may be accomplished by a glaze comprising: 82.60%xc2x15% of frit, 1.31-10.31% of a first flux, 1.20-7.20% of a second flux, 0.46-1.06% of a thickener and 4.91-15.91% of a phosphorus pigment. In the preferred embodiment, the first flux is Lithium Carbonate, the second flux is Borax, and the thickener is a Cellulose Gum such as carboxmethylceullulose.
To improve the glaze a suspending agent, like Bentonite, and a suspension agent, like Magnesium Sulfate, may be used. Preservatives and deflocculants can be used to improve efficacy.